Michal Majek

Comenius University Bratislava · Department of Organic Chemistry

The Front Cover portrays a phenanthrolimidazole molecule (a known electrochemical mediator) as a hiker crossing the boundaries between the fields of electro‐ and photocatalysis. The scene illustrates a systematic approach toward harnessing electrochemical mediators for photocatalysis, which is presented by M. Májek, R. D. Little, R. Francke and co‐...

Arylboronates are helpful building blocks in organic synthesis. Here, we present an efficient mechanochemical synthesis of arylboronates from arene diazonium salts. Importantly, this transformation was significantly enhanced by sodium chloride, which probably promotes the decomposition of diazonium salts via anion exchange. Chloride anions also par...

In view of the frequently cited similarities between photo‐ and electrocatalysis, large overlaps are to be expected in terms of the mediators used. However, closer inspection reveals that the exchange of mediators is the exception rather than the rule. In this context, the mediator portfolio of electrosynthesis holds great potential for useful appl...

We report a Suzuki 2,2'-diarylation of the racemic 2,2'-diiodo-1,1'-binaphthyl which proceeds with deracemization via a pallada(IV)cyclic intermediate, induced by a simple chiral ligand─BINAP [2,2'-bis(diphenylphosphino)-1,1',-binaphthyl]. A systematic study of the reaction scope, using 45 arylboronic acids, reveals that the diarylated product is f...

Mimicking nature's efficiency and sustainability in organic chemistry is a major goal for future chemists; redox reactions are a key element in a variety of fields ranging from synthesis and catalysis to materials chemistry and analytical applications. Sustainability is increasingly becoming a consideration in synthesis and functional chemistry and...

DOI: https://doi.org/10.1021/acs.joc.1c00561

A robust method based on NMR traceable cyclic intermediates clearly distinguished self-immolation from other cargo-release processes.

A photocatalytic synthesis of 1,5-diaryl pyrazoles from arenediazoniums and arylcyclopropanols is reported. The reaction proceeded under mild conditions (rt, 20 min) with catalytic [Ru(bpy)3]2+ under blue-light irradiation and exhibited compatibility with several functional groups (e.g., I, SF5, SO2NH2, N3, CN) and perfect levels of regiocontrol. M...

The facilitation of redox-neutral reactions by electrochemical injection of holes and electrons, also known as 'electrochemical catalysis', is a little explored approach that has the potential to expand the scope of electrosynthesis immensely. To systematically improve existing protocols and to pave the way toward new developments, a better underst...

Hypervalent iodine compounds constitute a popular class of reagents in organic chemistry. Regardless of whether they are generated in situ from an iodoarene precursor with a terminal oxidant or used in stoichiometric amounts, the resulting separation and waste issues are major challenges en route to sustainable and scalable processes. The electroch...

The photo-oxygenation of versatile arylcycloalkenes proceeds through zwitterionic intermediates and provides access to new allyl hydroperoxides and endoperoxides.

Photocatalytic bond activations are generally limited by the photon energy and the efficiency of energy and electron transfer processes. Direct two-photon processes provide sufficient energy but the ultra-short lifetimes of the excited states prohibit chemical reactions. The commercial dye 9,10-dicyanoanthracene enabled photocatalytic aromatic subs...

Trifluoromethyl aryl sulfides (Ar-SCF3) constitute highly attractive building blocks due to their exceptional lipophilicity and chemical properties. Related protocols of radical aromatic trifluoro-methylthiolation of arenediazonium salts were developed that are based on the facile generation of intermediate aryl radicals. Their reactions with comme...

Aromatic thioethers and analogous heavier chalcogenides were prepared by reaction of arene-diazonium salts with disulfides in the presence of the cheap and weak base NaOAc. The mild and practical reaction conditions (equimolar reagents, DMSO, r.t., 8 h) tolerate various functional groups (e.g. Br, Cl, NO2, CO2R, OH, SCF3, furans). Mechanistic studi...

Visible light photoredox catalysis enables the efficient synthesis of arenesulfonyl chlorides from anilines. The new protocol involves the convenient in situ preparations of arenediazonium salts (from anilines) and the reactive gases SO2 and HCl (from aqueous thionyl chloride). The photocatalytic chlorosulfonylation operates at mild conditions (roo...

Photoredox catalysis has emerged as a powerful tool for the utilization of visible light to drive chemical reactions between organic molecules that exhibit two rather ubiquitous properties: colorlessness and redox-activity. The photocatalyst, however, requires significant absorption in the visible spectrum and reversible redox activity. This very g...

The activation of aryl-Br bonds was achieved by sequential combination of a triplet-triplet annihilation process of the organic dyes, butane-2,3-dione and 2,5-diphenyloxazole, with a single-electron-transfer activation of aryl bromides. The photophysical and chemical steps were studied by time-resolved transient fluorescence and absorption spectros...

The synthesis of benzoates from arene diazonium salts, carbon monoxide, and alcohols in the presence of eosin Y as photocatalyst is presented.

The defunctionalization of anilines is an important strategy in aromatic-substitution chemistry. Herein, we report on visible light mediated hydro- and deuterodediazonations in solutions of DMF. The mild reaction conditions (DMF, RT, no additives) tolerate various functional groups and allow the site-specific introduction of D atoms to the arene. M...

Synthesen von Benzoesäureestern aus Kohlenmonoxid und Arylelektrophilen zählen zu den bedeutendsten übergangsmetallkatalysierten Carbonylierungen und finden vielfältige Anwendung in Forschung und Produktion. Diese Reaktionen laufen unter Pd- oder Ni-Katalyse in Gegenwart geeigneter Liganden und stöchiometrischer Mengen Base ab. Wir haben ein altern...

The synthesis of benzoates from aryl electrophiles and carbon monoxide is a prime example of a transition-metal-catalyzed carbonylation reaction which is widely applied in research and industrial processes. Such reactions proceed in the presence of Pd or Ni catalysts, suitable ligands, and stoichiometric bases. We have developed an alternative proc...

A combined spectroscopic, synthetic, and apparative study has allowed a more detailed mechanistic rationalization of several recently reported eosin Y-catalyzed aromatic substitutions at arenediazonium salts. The operation of rapid acid-base equilibria, direct photolysis pathways, and radical chain reactions has been discussed on the basis of pH, s...

Ans Licht gebracht: Die Wiederentdeckung von sichtbarem Licht als unerschöpfliche Energiequelle für organische Reaktionen hat kupferkatalysierte Kupplungen wieder in den Mittelpunkt des Interesses gerückt. Dieses Highlight fasst die wichtigsten Entwicklungen bei C-C- und C-N-Kupplungen zusammen, in denen kovalent gebundene Substrat-Kupfer-Komplexe...

Photo-sensitized synthesis of arylsulfides from arenediazonium salts in the presence of eosin Y has been developed. This protocol exhibits high functional group tolerance and a wide substrate scope and is an attractive alternative to the thermal reaction that involves explosive intermediates.

Bringing to light: The rediscovery of visible light as an abundant energy source for organic reactions has most recently brought copper-catalyzed coupling reactions to the center of attention. This Highlight summarizes the most significant advancements in the field of CC and CN coupling reactions in which covalent copper-substrate complexes are p...